To overcome some of the disadvantages of repeated venipuncture injections, implantable infustate injection ports were developed. Such devices provide a bolus or therapeutic dose of the drug contained therein to a particular location within the patient's body. To replenish the drug in the implanted device, a subcutaneous device can be provided in fluid communication with the drug delivery device, such as provided in U.S. Pat. No. 5,137,529, incorporated herein by reference. These implantable devices typically include an internal chamber, a penetrable self-sealing septum, and a hollow male outlet connector, which are subcutaneously implanted within the patient.
The outlet connector is attached to a catheter element or drug delivery tube for transmitting drugs from the internal chamber to a predetermined area of the patient's body, such as a cavity, a large vein, a tumor, or an injury site. Once installed, the internal chamber can be periodically filled with drug by inserting a hypodermic needle through the patient's skin and the septum to permit injection of the drug into the internal chamber. Devices of this general type can be effectively utilized for dispensing drug in the body of a patient over a prolonged period of time since the injection port provides a means for administering additional medicament into the device by means of a syringe inserted into the injection port.
Typically, such devices utilize pumps of one form or another. That is, they are designed to pump the drug from a reservoir through a tube to a site in the body. One of the disadvantages of such systems is that there is a net change in volume in the reservoir and/or the receptor. This net change in volume is undesirable where, for example, a drug is being delivered to an area such as the brain where slight volume changes can cause a large change in intracranial pressure.
Another problem encountered by conventional devices is device leakage. U.S. Pat. No. 4,857,053 to Dalton, for example, discloses that drug delivery ports utilizing elastomeric materials, such as silicon rubber, as the penetrable wall material tend to develop leaks.
Therefore, a need exists for an implantable, refillable, rate controlled leak-proof drug delivery device that does not rely on pressure to drive a drug from the device.